Many different types of filters are available to consumers. Determining which type is most appropriate for you—or whether you need a filter at all—depends on what functions you want a filter to provide. No filter eliminates all contaminants, so understanding what filters do and do not do is important.

What does the filter remove?

Read the label to see if it is NSF-certified. If it is, you can search NSF’s databaseExternal to learn more about what a particular model is certified to protect you against. Labels on water filters also typically state the contaminants that are reduced, which can help to guide your choice. Be sure to read labels carefully yourself and verify the manufacturer’s claims with an independent source, as not all sales representatives will be familiar with your needs.

Keep in mind that most brands include many different types of filters. Sales people might be able to help you make an appropriate selection, but remember that they are sometimes paid to sell a particular brand. You should check claims and read the fine print on filter packaging for yourself and ensure that it will work for your purposes before purchasing.

Don’t assume that if the filter removes one contaminant, it also removes others. Filters that remove chemicals often do not effectively remove germs, and vice versa. Some water treatment devices that remove chemicals, such as reverse osmosis, ion exchange, or distillation systems, might also remove fluoride. Children who drink water with levels of fluoride <0.6 ppm might need a fluoride supplement. Check with your child’s pediatrician or dentist for specific recommendations.

How much does the system cost?

The prices of different filtration systems can vary widely, from simple systems that can cost under $20 to complex systems costing hundreds of dollars and requiring professional installation. In addition to the price of purchasing and installing the system, consider the cost, schedule, and ease of maintenance, such as changing filter cartridges. In order to continue to work properly, all water treatment systems require maintenance.

How much filtered water do you need?

Some filters are slow, while others can filter large amounts of water quickly. If you only need the filter for personal drinking water, you may not need a fast filter.

What kind of system do you need, and how does it fit into your home?

Filters commonly found in homes and stores include water filter pitchers, end-of-tap or faucet-mounted filters, faucet-integrated (built-in) filters, on-counter filters, under-sink filters, and whole-house treatment units. No filters or treatment systems are 100% effective in removing all contaminants from water, and you need to know what you want your filter to do before you go shopping (see Step 1). Not all filters of a particular type use the same technology, so you should read the label carefully.

Water filter pitchers

Water filter pitchers are pitchers that are filled from the top and have built-in filters that water must pass through before being poured out for drinking or other use.

Faucet-integrated filtration systems are faucets designed with built-in filters (instead of an attached filter, like a faucet-mounted system) and require installation.

Pros: Can easily switch between filtered and unfiltered water

Cons: Often expensive, require installation

On-counter filters

Faucet-integrated filtration systems are faucets designed with built-in filters (instead of an attached filter, like a faucet-mounted system) and require installation.

Pros: Can easily switch between filtered and unfiltered water

Cons: Often expensive, require installation

Under-sink filters

Under-sink filtration systems are installed under a sink and send water through a pipe to the filter’s own specially installed faucet.

Pros: Filter large amounts of water, do not take up countertop space

Cons: Often expensive, may require modifications to plumbing

Whole-house water treatment

Whole-house water treatment devices treat all water entering the house, not just the water used for drinking.

Pros: Treatment is applied to all water entering your home, which may be important for hard water and volatile organic compounds (VOCs)

Cons: Often expensive, may require modifications to plumbing, may require professional maintenance, filtering that removes chlorine might increase growth of germs in all the pipes in your house

Treatment devices

This table shows some benefits and limitations of a few popular home water treatment technologies. It does not include information on all filter types including many those that might remove germs via simple pore size filtration. Also see Technical Information on Home Water Treatment Technologies.